Another victim from attacks on U.N.-backed anti-polio teams in Pakistan died on Thursday, bringing the three-day death toll in the wave of assaults on volunteers vaccinating children across the country to nine, officials said.

Hilal Khan, 20, died a day after he was shot in the head in the northwestern city of Peshawar, said health official Janbaz Afridi

Since Monday, gunmen had launched attacks across Pakistan on teams vaccinating children against polio. Six women were among the nine anti-polio workers killed in the campaign, jointly conducted with the Pakistani government.

The U.N. World Health Organization suspended the drive until a government investigation was completed.

U.N. Secretary-General Ban Ki-moon called the killings “cruel, senseless and inexcusable.” Speaking at his year-end news conference Wednesday, Ban said the victims were among thousands across Pakistan “working selflessly to achieve the historic goal of polio eradication.”

The suspension of the vaccinations was a grave blow to efforts to bring an end to the scourge of polio in Pakistan, one of only three countries where the crippling disease is endemic.

Azmat Abbas, with UNICEF in Pakistan said the field staff would resume the work when they have a secure working environment.

“This is undoubtedly a tragic setback, but the campaign to eradicate polio will and must continue,” Sarah Crowe, spokeswoman for UNICEF, said Wednesday.

However, local officials in the eastern city of Lahore continued the vaccination on Thursday under police escort, and extended the campaign with a two-day follow-up.

Deputy Commissioner Noorul Amin Mengal said about 6,000 Pakistani government health workers were escorted by 3,000 police as they fanned out across the city.

“It would have been an easy thing for us to do to stop the campaign,” he said. “That would have been devastating.”

No one has claimed responsibility for the attacks but some Islamic militants accuse health workers of acting as spies for the United States and claim that the vaccine makes children sterile.

Taliban commanders in the country’s troubled northwest tribal region have also said the vaccinations can’t go forward until the U.S. stops drone strikes in Pakistan.

The insurgent opposition to the campaign grew last year, after it was revealed that a Pakistani doctor ran a fake vaccination program to help the CIA track down and kill Al Qaeda founder Usama bin Laden, who was hiding in the town of Abbottabad in the country’s northwest.

Prevention efforts against polio have managed to reduce the number of cases in Pakistan by around 70 percent this year, compared to 2011, but the recent violence threatens to reverse that progress.

Pakistanis for Peace Editor’s Note– Less than a week since the tragedy in Newtown Connecticut and the death of so many innocent children, we see the ill effects of the Dr Shakil Afridi incident whereby undercover CIA agents using Pakistani doctor under the guise of a polio vaccination program infiltrated and eventually found where OBL was being hidden. The great thing was that we got and killed the bastard.

The negative consequences of this however is now evident as we risk putting up to 33 million Pakistani children in harm’s way as they may not get their polio vaccinations due to Taliban distrust of any medical worker as being a foreign agent. These are horrible consequences and 1 life is not worth 33 million. Very dismayed with the current situation and hoping the Pakistani and American governments can provide better security to all medical teams and doctors if the Pakistani children are to get their critical polio vaccines.